A multimillion dollar problem for the citrus industry worldwide is the formation of bitterness in citrus juice within hours after extraction of the juice from the fruit. The primary cause of such delayed bitterness is the formation of the bittering agents limonoids and flavonoids. In oranges, lemons and tangerines, the principal limonoids are limonin and nomilin Grapefruit principally contains the flavonoid naringin, with a minor amount of nomilin. A number of methods have been developed to reduce or extract such bittering agents, including preharvest treatment by an auxin plant growth regulator to inhibit nomilin biosynthesis, supercritical carbon dioxide extraction of limonin at 4000 psi, extraction of naringin and limonin from grapefruit with cross-linked polystyrene resin monomers (U.S. Pat. No. 4,514,427), and adsorption of both bittering agents and acid with a lignin-type adsorbent derived from carob seed (U.S. Pat. No. 4,282,264). Each of these methods has drawbacks, e.g., auxin plant growth regulators are expensive, high pressure supercritical extraction is highly energy-consuming, and adsorption of acid components along with bittering agents deleteriously affects flavor. The primary solution to the bitterness problem has been to simply blend excessively bitter juice (containing &gt;12 ppm limonin) with non-bitter juice (&lt;6 ppm limonin).
There is therefore still a need in the art for a bittering agents removal process that is selective, simple, efficient, inexpensive and that has no impact on the flavor of the citrus juice These needs and others are met by the present invention, which is summarized and described in detail below.